/*_############################################################################
  _## 
  _##  SNMP4J 2 - ByteArrayWindow.java  
  _## 
  _##  Copyright (C) 2003-2011  Frank Fock and Jochen Katz (SNMP4J.org)
  _##  
  _##  Licensed under the Apache License, Version 2.0 (the "License");
  _##  you may not use this file except in compliance with the License.
  _##  You may obtain a copy of the License at
  _##  
  _##      http://www.apache.org/licenses/LICENSE-2.0
  _##  
  _##  Unless required by applicable law or agreed to in writing, software
  _##  distributed under the License is distributed on an "AS IS" BASIS,
  _##  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  _##  See the License for the specific language governing permissions and
  _##  limitations under the License.
  _##  
  _##########################################################################*/
package org.snmp4j.security;

/**
 * The <code>ByteArrayWindow</code> provides windowed access to a subarray
 * of a byte array.
 * @author Frank Fock
 * @version 1.0
 */
public class ByteArrayWindow {

    private byte[] value;
    private int offset;
    private int length;

    /**
     * Creates a byte array window that provides access to the bytes in the
     * supplied array between the position starting at the supplied offset.
     * @param value
     *    the underlying byte array.
     * @param offset
     *    the starting position of the created window.
     * @param length
     *    the length of the window.
     */
    public ByteArrayWindow(byte[] value, int offset, int length) {
        this.value = value;
        this.offset = offset;
        this.length = length;
    }

    public byte[] getValue() {
        return value;
    }

    public void setValue(byte[] value) {
        this.value = value;
    }

    public int getOffset() {
        return offset;
    }

    public void set(int i, byte b) {
        if (i >= length) {
            throw new IndexOutOfBoundsException("" + i + " >= " + length);
        }
        if (i < 0) {
            throw new IndexOutOfBoundsException("" + i);
        }
        this.value[i + offset] = b;
    }

    public byte get(int i) {
        if (i >= length) {
            throw new IndexOutOfBoundsException("" + i + " >= " + length);
        }
        if (i < 0) {
            throw new IndexOutOfBoundsException("" + i);
        }
        return value[i + offset];
    }

    public int getLength() {
        return length;
    }

    /**
     * Indicates whether some other object is "equal to" this one.
     *
     * @param obj the reference object with which to compare.
     * @return <code>true</code> if this object is the same as the obj argument;
     *   <code>false</code> otherwise.
     */
    public boolean equals(Object obj) {
        if (obj instanceof ByteArrayWindow) {
            ByteArrayWindow other = (ByteArrayWindow) obj;
            if (other.length != length) {
                return false;
            }
            for (int i = 0; i < length; i++) {
                if (other.value[i] != value[i]) {
                    return false;
                }
            }
            return true;
        }
        return false;
    }

    public boolean equals(ByteArrayWindow other, int maxBytesToCompare) {
        if ((other.length < maxBytesToCompare) || (length < maxBytesToCompare)) {
            return false;
        }
        for (int i = 0; i < maxBytesToCompare; i++) {
            if (value[offset + i] != other.value[other.offset + i]) {
                return false;
            }
        }
        return true;
    }
}
